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Blind, by definition – or should we prefer functional vision?

2010; Wiley; Volume: 88; Issue: 2 Linguagem: Inglês

10.1111/j.1755-3768.2010.01885.x

1755-3768

Tero Kivelä,

Glaucoma and retinal disorders

In the review entitled ‘Assessment of functional vision and its rehabilitation’, published in this issue of Acta Ophthalmologica, Dr August Colenbrander – a Senior Scientist of Dutch origin affiliated with the Smith-Kettlewell Eye Research Institute of San Francisco, California – cites the following provocative statement: ‘More people are blinded by definition than by any other cause’ (Colenbrander 2010). This statement is attributed to Lieutenant Lloyd H. Greenwood, the spirited first Executive Director of the Blinded Veterans Association of the United States, commenting on the term legal blindness back in 1949 (Ritter 1957). Greenwood was blinded by a German FlaK anti-aircraft gun, Fliegerabwehrkanone, when piloting his Consolidated B-24 Liberator heavy bomber over Vienna, Austria, during Word War II (Koestler 1976). Sixty years later, his statement continues to provoke divergent opinions. Dr Colenbrander would be happy if legal blindness be largely replaced with low vision in everyday parlance. He perceives a hidden connotation in the expression ‘you are blind’ as compared with ‘you have low vision’– the former sounds permanent, whereas the latter leaves the way open for vision rehabilitation. Although many would agree, not everyone shares his opinion. One comment received during peer review was: ‘We should not reinforce the ancient social stigma attached to blindness and should not try to draw a line between blindness and low vision: rehabilitation strategies should be recommended on the basis of what is practical and best achieves the patient’s goals.’ Truly enough, the states of being blind and having low vision are associated with diverging, but not mutually exclusive, compensatory strategies that can be employed to function as efficiently as possible. The pragmatist points out that by reverting to vision substitution skills primarily offered to the blind, such as walking with a long cane or reading Braille, at least some patients with low vision might be able to function more efficiently than their peers with identical visual impairment who use only vision enhancement strategies like magnifying aids. On closer scrutiny, the apparently diverging opinions of Dr Colenbrander and the reviewer are not as far removed as they sound on first hearing: both like to view visual loss as a continuum. It should be evident by now that Dr Colenbrander’s essay is not a traditional review. It can best be categorized as a chimera between a review and an editorial. As such it makes interesting and rewarding reading. A key issue in Dr Colenbrander’s essay is drawing a distinction between visual functions measured clinically – which translate to how the eye functions – and patient abilities and functional vision typically measured by questionnaires (Massof & Ahmadian 2007) – which translate to how the person functions – and further differentiating these two from the assessment of quality of life – which even involves the societal level (Massof 2008). This is a useful distinction to make, because it may help the comprehensive ophthalmologist to capture terms that are variously and sometimes confusingly used by experts in low vision and vision rehabilitation. For example, the current literature frequently expands the term visual function to include reading, mobility and other vision-dependent abilities measured with ‘visual function questionnaires’. As Dr Colenbrander points out, such questionnaires often mix items that assess visual function with others that assess functional vision, according to the framework that he favours. Indeed, inconsistent use of the term visual function is one unfortunate but avoidable obstacle for penetration of the concept of functional vision to private practices, outpatient clinics and wards not primarily involved with vision rehabilitation. Similar to the Birmingham Eye Trauma Terminology, a classification which stemmed from the inconsistent use of terms such as perforating eye injury and eventually resulted in widely accepted guidelines for authors (Kuhn et al. 1996, 2002), a common agreement on standard terminology would solve the problem, given enough time. The clear distinction between visual function and functional vision as outlined by Dr Colenbrander provides a useful conceptual framework for ophthalmologists which will help them to comprehend the value of assessing functional vision and of communicating it to administrators and policy makers whose task is to allocate money and resources in health care. Currently, measures of visual functions dominate most policies controlling access to care and social benefits. For example, uniform criteria for access to elective surgical care were introduced in Finland in March 2005 as part of a national health care reform. The primary criteria defining access to cataract surgery were set to 20/40 vision or less in the better eye or 20/60 vision or less in the worse eye. These criteria are clear cut and easy to apply, but are they truly the best available for defining who will benefit from swift surgery and whose treatment can be deferred? Let us draw from a trial which enrolled 507 consecutive patients scheduled for bilateral cataract surgery (Kivelä et al. 2006). All patients completed one widespread measure of functional vision, the Visual Function Index VF-14 (Steinberg et al. 1994) in its original and in a shortened form (Uusitalo et al. 1999). The questionnaire was designed and thoroughly validated for assessing functional vision of patients with cataract (Steinberg et al. 1994). It consists of 14 items which address everyday visual tasks. The respondent chooses an answer that corresponds to the level of difficulty he or she has in performing each task, ranging from no difficulty to being unable to perform the task. Of the 507 patients who all fulfilled the visual acuity criteria for being admitted to cataract surgery, 14% got a score 90 or better, indicating negligible difficulty in performing their everyday visual tasks. A population of patients also exist whose visual acuity exceeds the current national criteria for access to elective cataract surgery but whose VF-14 score is low. These patients most likely are more in need of surgery than the former group of patients who fulfill the national criteria. It is unlikely that cataract surgery is an exception in which assessment of functional vision likely would help to allocate health care resources more rationally. Recognizing the importance of functional vision, the International Council of Ophthalmology (2008) has adopted the statement: ‘Ophthalmic care extends beyond the treatment of eye disease to promoting the well being of the patient. Treatment decisions should consider patient needs and ascertain that the clinician’s expectations match those of the patient. Studies of ophthalmic outcomes should likewise include appropriate tools to evaluate visual functioning. These principles should feature prominently in ophthalmic training, ophthalmic practice and in health care policy decisions’. How should this resolution influence your practice and the organization that you work for or are responsible of? A rational starting point for formulating your answer is to read and digest Dr Colenbrander’s review. You do not need to accept all of his viewpoints, but you should definitely be aware of them. Functional vision has come of age and portends to become one megatrend of the beginning decade of eye care.